Organic Chemistry Examples in Chemistry

Start with the recap, study the fully worked examples, then use the practice problems to check your understanding of Organic Chemistry.

This page combines explanation, solved examples, and follow-up practice so you can move from recognition to confident problem-solving in Chemistry.

Concept Recap

Organic chemistry is the study of carbon-containing compounds, especially those built from carbon-hydrogen frameworks and modified by functional groups.

Carbon can build huge families of compounds, so chemists study those compounds as a major branch of chemistry.

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How to Use These Examples

  • Read the first worked example with the solution open so the structure is clear.
  • Try the practice problems before revealing each solution.
  • Use the related concepts and background knowledge badges if you feel stuck.

What to Focus On

Core idea: Organic Chemistry starts by identifying the carbon skeleton, functional group, and repeating pattern if present.

Common stuck point: Students often know a formula related to organic chemistry but skip the recognition step: Am I using carbon structure, bonds, functional groups, or repeating units to explain the molecule? That leads to a correct-looking substitution attached to the wrong chemical model.

Sense of Study hint: Ask: Am I using carbon structure, bonds, functional groups, or repeating units to explain the molecule?

Worked Examples

Example 1

medium
Balance the complete combustion of butane: C4H10+O2→CO2+H2OC_4H_{10} + O_2 \rightarrow CO_2 + H_2O.

Answer

2C4H10+13O2→8CO2+10H2O2C_4H_{10} + 13O_2 \rightarrow 8CO_2 + 10H_2O

First step

1
Balance C: each C4H10C_4H_{10} gives 4 CO2CO_2, so put 8 CO2CO_2 for 2 butanes.

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Example 2

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Balance: C2H4+O2→CO2+H2OC_2H_4 + O_2 \rightarrow CO_2 + H_2O (combustion of ethene).

Example 3

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Determine the empirical formula of a hydrocarbon that is 80.0% C and 20.0% H by mass.

Example 4

hard
How many grams of CO2CO_2 are produced from burning 32.0 g of methane completely? (C = 12.0, H = 1.0, O = 16.0)

Example 5

hard
Determine the molecular formula of a hydrocarbon with empirical formula CH2CH_2 and molar mass 56 g/mol.

Example 6

challenge
Combustion of 4.40 g of an unknown alkane produces 13.20 g of CO2CO_2. Identify the alkane.

Practice Problems

Try these problems on your own first, then open the solution to compare your method.

Example 1

easy
Organic chemistry is the study of compounds containing which element?

Example 2

easy
Is methane (CH4CH_4) an organic compound?

Example 3

easy
How many bonds does a carbon atom typically form?

Example 4

easy
Which is NOT typically classified as organic: CO2CO_2 or C2H6C_2H_6?

Example 5

easy
What two products always form when a hydrocarbon burns completely?

Example 6

easy
Does the structure of an organic molecule affect its properties?

Example 7

easy
The carbon backbone of an organic molecule is also called its what?

Example 8

easy
Are sugars and proteins organic compounds?

Example 9

medium
Ethanol (C2H5OHC_2H_5OH) and dimethyl ether (CH3OCH3CH_3OCH_3) share the formula C2H6OC_2H_6O but differ greatly. What does this illustrate about organic chemistry?

Example 10

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Write the balanced equation for the complete combustion of methane, CH4CH_4.

Example 11

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Why can carbon form millions of different compounds while most elements form few?

Example 12

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A label calls a carbon-free mineral salt 'organic produce.' Why is this not the chemistry meaning of organic?

Example 13

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Classify each as organic or inorganic: glucose (C6H12O6C_6H_{12}O_6), table salt (NaClNaCl), propane (C3H8C_3H_8).

Example 14

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Two compounds have the same molecular formula but react very differently. What can you conclude about them?

Example 15

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Why does organic chemistry get its own branch separate from inorganic chemistry?

Example 16

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Why do organic compounds generally have lower melting points than ionic compounds like NaClNaCl?

Example 17

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Name two reasons carbon is uniquely suited to building life's molecules.

Example 18

challenge
Complete combustion of propane is C3H8+5O2→3CO2+4H2OC_3H_8 + 5O_2 \rightarrow 3CO_2 + 4H_2O. If 2 mol of propane burns, how many moles of CO2CO_2 form?

Example 19

challenge
Balance the complete combustion of ethane: C2H6+O2→CO2+H2OC_2H_6 + O_2 \rightarrow CO_2 + H_2O.

Example 20

challenge
Glucose (C6H12O6C_6H_{12}O_6) ferments to ethanol and carbon dioxide: C6H12O6→2C2H5OH+2CO2C_6H_{12}O_6 \rightarrow 2C_2H_5OH + 2CO_2. Verify the equation is balanced by checking each element.

Example 21

easy
Which functional group is present in ethanol, C2H5OHC_2H_5OH?

Example 22

easy
What is the general molecular formula for an alkane with nn carbons?

Example 23

easy
How many hydrogens are in butane, C4H?C_4H_{?}, using the alkane formula?

Example 24

easy
Does the compound COCO (carbon monoxide) fit the everyday definition of an 'organic compound' used in chemistry?

Example 25

easy
Is the compound benzene, C6H6C_6H_6, an organic compound?

Example 26

medium
Pentane and 2-methylbutane share the formula C5H12C_5H_{12} but boil at different temperatures. What relationship do they share?

Example 27

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How many structural isomers of C4H10C_4H_{10} are there?

Example 28

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Classify each functional group: −NH2-NH_2, −CHO-CHO, −COOH-COOH.

Example 29

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What is the molar mass of methane CH4CH_4? (C = 12.0, H = 1.0 g/mol)

Example 30

medium
Why are most organic compounds insoluble in water?

Example 31

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A compound has the formula C3H6OC_3H_6O and reacts as an aldehyde. Name a likely structure.

Example 32

medium
Which has more carbon-carbon bonds: ethane (C2H6C_2H_6) or octane (C8H18C_8H_{18})?

Example 33

medium
Are amino acids organic compounds?

Example 34

hard
How many structural isomers of pentane (C5H12C_5H_{12}) exist?

Example 35

hard
A 0.50 mol sample of ethanol C2H5OHC_2H_5OH burns completely. How many moles of water form? (C2H5OH+3O2→2CO2+3H2OC_2H_5OH + 3O_2 \rightarrow 2CO_2 + 3H_2O)

Example 36

hard
Ethanol and dimethyl ether are isomers of C2H6OC_2H_6O. Which has the higher boiling point and why?

Example 37

hard
Calculate the percent by mass of carbon in glucose, C6H12O6C_6H_{12}O_6 (M = 180.0 g/mol).

Example 38

hard
Why does propanoic acid (CH3CH2COOHCH_3CH_2COOH) dissolve in water while pentane does not?

Example 39

challenge
A 22.4 L sample of methane at STP burns completely. What volume of O2O_2 at STP is required?

Example 40

challenge
Polyethylene is made from ethylene monomers (C2H4C_2H_4). What is the empirical formula of polyethylene, and what is its repeating unit?
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Background Knowledge

These ideas may be useful before you work through the harder examples.

chemical bondvalence electron